This invention relates to MOSFET devices and more specifically relates to a novel MOSFET structure and process for its manufacture which makes the device more capable of operation in a high radiation environment.
Semiconductor devices, and particularly power MOSFETs, require special manufacturing techniques to permit their operation in high radiation environments such as, but not limited to, those encountered in outerspace environments such as orbiting satellites. U.S. Pat. Nos. 5,338,693 and 5,475,252 in the names of Merill and Spring, and patent application Ser. No. 09/020,837, filed Feb. 9, 1998 (IR 1444) in the names of Boden and Xu describe such MOSFETS.
The present invention is for a lower voltage (250 volts or lower) xe2x80x9crad hardxe2x80x9d MOSFET in which an ultrashallow channel or base region is employed. The depth of the new base is reduced to about 1.3 microns as compared to known devices employing a depth of 3.0 microns. A striped base pattern, rather than a cellular pattern is also preferably employed.
It has been found that the new device has a 50% improvement in total dose radiation resistance, as compared to prior art devices. Further, a reduced mask count process (7 masks instead of 9 masks) is also employed.